An understanding of the process of membrane assembly is critical to many areas of biomedical research. Bacteria are useful model systems for the study of cellular phenomena. The photosynthetic bacterium Rhodospirillum rubrum forms a differentiated photosynthetic membrane under certain growth conditions and provides an excellent opportunity to study the process of membrane assembly. R. rubrum is an experimentally accessible system because: 1) the photosynthetic membrane has a simple protein composition consisting mainly of the photochemical components; 2) the formation of the photochemical complexes and the assembly of the photosynthetic membrane can be experimentally manipulated; 3) functional assembly of these components can be assessed on the basis of spectroscopy and the capacity for phototrophic growth; 4) membranes are readily isolated from this organism; 5) nonphotosynthetic mutants are viable because they can grow chemotrophically; and 6) the photochemical components are among the most well studied of membrane protein structures. Our long-term goal is to examine the events in the assembly of membrane protein complexes using the photochemical components of R. rubrum as a model system. In this work, the assembly of the photochemical components and the role of putative proteins encoded within the photosynthetic gene cluster will be investigated by the construction, complementation and characterization of mutants. These studies will help to define the mechanism and requirements for the assembly of these membrane-protein complexes. This work is based on the results of previous studies and enabled by the expression vector we have developed. This work will lead to an enhanced understanding of the process of membrane protein assembly.